Ruthenium films and ruthenium-containing films, such as SrRuO and RuO2, have been used for several parts in semiconductor devices such as metal electrode and Cu seed layer. The resistivity of ruthenium is lower than that of Ir and Pt. Additionally, RuO2 has better conductivity than the two corresponding Ir and Pt metal oxides, which is important when the deposited metal layer is contacted with oxidizing agents (e.g., O2, O3) during subsequent processes. As the size of chip becomes smaller, each layer must be thinner. Therefore chemical vapor deposition (CVD) and preferably atomic layer deposition (ALD) techniques are desired and precursors which can be used in CVD and ALD mode are also desired.
A large variety of ruthenium complexes are available and some have been studied in CVD or ALD mode. However, most of them have drawbacks, such as low vapor pressure and/or deposition of films exhibiting high impurity contents (C and O in most of the cases), long incubation time, poor adherence, and non-uniformity in deep trenches. Besides, some precursors are not liquid and need to be dissolved in a solvent or mixture of solvents to allow an easy delivery of the vapors to the reaction chamber.
Tricarbonyl ruthenium products were reported as CVD/ALD precursors (see, e.g., U.S. Pat. Nos. 6,517,616 and 6,897,160 and JP2002-212112). PCT Publication No WO2008/034468 discloses (Rn—CHD)Ru(CO)3 precursors, wherein R is selected from the group consisting of C1-C4 linear or branched alkyl, alkylamides, alkoxides, alkylsilyamides, amidinates, carbonyl, and/or fluoroalkyl substituents and n may range from 1 to 8.
A need remains for ruthenium-containing precursors having properties suitable for vapor deposition.